Lubricating greases



Patented Dec. 25, 1945 UNITED STATES PATENT orrlca wnnlca'rmc oanssssJohn D. Morgan, South Orange, N. 1., aalg'nor to Cities Service OilCompany, New York, N.Y., a corporation of Pennsylvania No Drawing. YApplication October 16, 1942,

' Serial N0. 462,221

12 Claims.

This invention relates to improvements in lubricants and moreparticularly to lubricating greases containing a liquid lubricating oilor medium and a silver soap.

I have discovered that silver soaps, for example, the soaps made fromsoap-iorming fatty materials such as the higher fatty acids, givelubricants of unusual properties which are quite difierent from thosemade from the usual alkali and alkaline earth metal soaps.

One of the serious problems of the present time is the provision ofsuitable greases for use at low temperatures. The ordinary greases madefrom mineral lubricating oils and sodium, calcium, alu- I minum, andother soaps, become hard and still and fail to lubricate at lowtemperatures, sometimes even at temperatures as low as zero degrees F.Greases containing silver soap have been found to be stable and plasticover relatively Example No. 1

A grease found to be useful at extremely low temperatures 01' the order01 about minus 70 F., was prepared by heating a mixture oi about 86parts a Ponca City lubricating oil stock, having a Saybolt Universalviscosity at 100 E01 72.5 seconds, and about 7.5 parts of silverstearate, to a temperature of 400 F. The mixture was heated gradually upto this temperature, and it was noted that at a temperatur of about 220F. the mixture began to turn to a blue-black color. The final mixturewas cooled. quickly in thin layers. A line. soft gel was produced.

This grease passed the Navy test for low temperature greases which isconducted with a ballbearing tester at a temperature oi minus 67' F. TheNavy limit for lowtemperature grease is thirty seconds ior onerevolution onthia tester, whereas the time recorded for the greasedescribed above was 20 seconds.

The silver stearate used in making the above grease was prepared byfirst making potassium stearate from KOH and stearic acid, and thenreacting the potassium stearate with silver nitrate. The resultingreaction mixture was ill- 5 state.

tassium nitrate. and finally dried in an oven at 220 F. The silver soapsare practically insoluble in water, and are preferably dispersed inliquid organic lubricants in a substantially dry Example N0. 2

, A slightly heavier grease was prepared by the procedure followed inExample No. 1, :by heating a mixture of 87.6 parts of the same minerallubrieating oil stock, 11.2 parts of silver stearate, and

1.4 parts 0! aluminum stearate. This grease also passed the Navy testfor a low temperature grease and was found-to have high load-carryingcharacteristics. In a test carried out on a 4-ball testing machine,there was no seizure up to and including a gage pressure-of 1000 lbs.,and only an eight division friction rise over the wholejpres s'urerange. This result is to be compared with a gage load of about 250 lbs.which is registered on the 4-ball machine at the point of seizure in thecase of a light Spindle oil.

- Example No. 3 A slightly modified grease from that of Example N0. 1was prepared from the same lubricating oil stock and silver stearate, byincluding in the mixture during the heating operation ,a smallproportion of a rubber latex. This mixture comprised about 85 parts orthe mineral lubricatin oil, about 8 parts oi. silver stearate, and aboutone part of rubber latex. The properties of this grease was similar tothat of Example No. 1 but it was found to be more adherent;

Light, medium or heavy greases may be made 3i! for particular purposesby varying the viscosity of the liquid lubricating oil, the quantity ofsilver soap, and the quantities of other constituents which may be addedto the compositions. The term "liquid lubricant or "lubricating oil" as40 used in connection with this invention, is not rein: properties.Examples of such compounds are:

trichiorobenzene, butyl oxalate, methyl benzoate.

butyl benzoate, butyl acetyl ricinoleate, amyl steal-ate, diethyl anddl-butyi phthalates, diamyl naphthalene, tributyl and tricresylphosphates,

$0 decalin, tetralin, normal hexyl ether, and halowaxoils. Many oi theseliquid lubricants'have been loud to be unusually eirective, even whenused alone at low temperatures, and their use is therefore especiallyeflective in making low temtered, the precipitate washed to remove anypdl5 perature greases with silver soaps.

While the invention has been illustrated-in connection with the use ofsilver stearate, other' silver soaps of fats or fatty acids may be used,such as silver laurate, silver oleate, silver palmitate, silverresinate, and silver soapsof whale oil, castor oil, etc. Most of thesesoaps have melting points in the neighborhood of about 200 C. In-makinggreases in accordance with the present invention the proportion ofsilver soap may be varied from 4% to or the composition, and thecomposition may, if desired, include from 1% .to 3% of an aluminum soapof one of the fatty materials mentioned above, such as aluminumstearate, and where rubber latex or equivalent elastic polymer is usedin the grease, it may comprise from 1% to 2% of the composition. Insteadof using rubber latex, synthetic rubbers may be used, or balata,chlorinated rubber, gum rubber, butyl rubber and others. The addition ofsmall proportions of silver soap to a lubricating liquid or oilincreases its load-carrying properties, prevents leakage from bearings,and improves the lubricating properties of the liquid or oil.

Any of the greases made in accordance with the present invention mayinclude a small proportion of an antioxidant or anticorrosion agentwhich may be -ound necessaryor advisable in the case of any particularliquid lubricating medium or particular bearing metals involved.Tributyl, triphenyl, and'tricresyl phosphites may be used as well asother known anticorrosion and antioxidizing agents.

It is to be understood that although the features of the invention havebeen described and illustrated in connection with certain specificexamples, the invention, however, it not to be limitedthereto orotherwise restricted, except by the prior art and the scope of theappended claims.

Having described the invention and illustrated the same in connectionwith certain specific examples, what is claimed as new is;

1. A lubricating composition having a grease structure made by heating amixture comprised principally of a lubricating oil and from about 4% toabout 20% by weight of a silver soap of a-higher fatty acid to atemperature of approximately 400 F., said composition having a stableplastic gel-like consistency.

2. A lubricating grease composition comprised principally ofapproximately 92 per cent .by weight of a mineral lubricating oil andapproximately 8 per cent by weight of silver stearate, said compositionhavin a stable plastic gel-like consistency resulting from the heatingofa mixture of said ingredients to a temperature of approximately 400 F.followed by cooling.

3. A lubricating grease composition comprised principally of a liquidlubricating medium, from approximately 4 to approximately 20 per cent byweight of a silver soap of soap-forming fatty material, and from one tothree per cent by weight of aluminum soap of a soap-forming fattymaterial, said composition having a stable plastic gel-like consistencyresulting from the heating or a mixture of said ingredients to atemperature of approximately 400 F. followed by cooling.

4. A lubricating grease composition having a plastic gel-likeconsistency made by heating a mixture of a liquid oily lubricant, asilver soap and an aluminum soap to a temperature of approximately 400F., said silver soap being the major grease-forming agent and beingpresent in the composition in sufficient proportion to substantiallythicken the liquid oily lubricant.

5. A lubricating grease composition having a plastic gel-likeconsistency and containing a major proportion of a liquid lubricatingoil, a substantial proportion of a silver soap of a soapforming fattymaterial serving as the major grease forming ingredient, a smallproportion of an aluminum soap and a small proportion of an elasticpolymer, said composition being formed by heating a mixture of saidingredient to stemperature of approximately 400 F. followed bysubsequent cooling.

6. The method of making a. silver soap grease comprising heating amixture comprised mostly of a liquid lubricating medium and fromapproximately'4% to approximately 20% by weight of a silver soap of asoap-forming fatty material to a temperature of approximately 400 F.,eflecting the heating operation gradually to the final temperature andthereafter quickly cooling the mixture in thin layers to produce astable plastic rease.

7. The method of making a silver soap grease as defined by claim 6 inwhich the initial mix .ture includes from about 1% to about 3% of analuminum soap of a soap-forming fatty material.

8. The method of making a silver soap grease 40 as defined by claim 6 inwhich the initial mixture includes a small proportion of an elasticpolymer sufllcient to increase the adherent properties of the resultinggrease.

. 9. The method of making silver soap grease as 45 defined by claim 6 inwhich a substantially dry silver soap is employed.

10. A lubricating grease composition in accordance with claim ,3 inwhich said silver soap is silver stearate.

11. A lubricating grease composition in accordance with claim 3 in which-said silver soap is silver stearate, and said aluminum soap is aluminumstearate.

12. A lubricating grease composition consisting 5.5 essentially ofapproximately 87.5, percent by weight of a mineral lubricating oil,about 11 per cent by weight of silver stearate, and about 1% per cent byweight of aluminum stearate, said composition having a stable plasticgel-like conno sistency resulting from the heating of the mixture ofsaid ingredients to a temperature of approximately 400 F. followed bycooling.

some n. MORGAN.

